Different weights of stone on weighing different media are given below.

Different weights of a piece of stone on weighing different media are given below.

media A = 30 N 

media B = 20 N 

media C = 25 N 

Which one of the above media are air, water and salt solution, find out the mass displaced by the stone, If 1 kg of stone is equal to 10N, calculate the mass of stone in air.